Modern homes require air conditioning, specifically, cooling in summer and heating in winter. The flow of fresh air is also necessary, in order to remove unwanted gases and odors. When the enthalpy gradient between outside and inside air is large, the flow of fresh air associated with energy consumption, for cooling in summer and heating in winter, increases. Thus, in tropical climates, where the outside air enthalpy is 90 kJ/kg and inside air is kept at 52 kJ/kg, the flow of fresh air required to exchange 1 kg of air increases the latent load by 38 kJ. Similarly, in the winter, the exchange of fresh air increases the heating load.